Electric connection between fixed and rotatable parts



y 1962 A. H. BOERDIJK ET AL 3,034,081

ELECTRIC CONNECTION BETWEEN FIXED AND ROTATABLE PARTS Filed June 25, 1957 vol/RAMA INVENTOR ARIE HENDRIK BOERDIJK JOHANNES MARTINUS HOLST AGENT art ice 3,034,081 Patented May 8, 1962 3,034,081 ELECTRIC CONNECTION BETWEEN FIXED AND ROTATABLE PARTS Ar e Hendrik Boerdiik and Johannes- Martinus Holst, Eindhoven, Netherlands, assignors to North American Philips. Company, Inc., New York, N.Y., a corporation of Delaware FiledJune 25', 1957', Ser. No. 667,859 Claims priority, application Netherlands July 21, 1956 Claims. (Ci. 339-6) The invention relates to an electric connection between twov relatively rotatable parts. 7

Such connections are known and usually consist of a brush provided in the stationary part and a rotatable part moving against this brush. This known connection is employed especially with electric motors and generators. They have the disadvantage that sparks may be struck between the rotatable part and the brush, so that fluctuations in the intensity of the electric current may occur. Particularly with acoustical apparatus, in which current intensity and/or voltage diflerences are employed for the conversion of air oscillations into, for example, magnetic or mechanical records or conversely, it is important to establish a very satisfactory electric contact between any relatively rotatable parts, since otherwise troublesome interference voltages occur.

One example of such an apparatus is a device for converting air oscillations into magnetic records or converse 1y, while the recording heads or the reproducing heads respectively perform a rotary movement. The recording or the reproducing of air oscillations with the aid of, for example, a microphone or a loudspeaker or the conversion of electric oscillations into magnetic records or of a record into a different kind of record require an electric connection between the rotating heads and a stationary part of the device, this connection being required to fulfill high demands. In this case, the known brush connection gives rise to troublesome irregularities during the conversion.

The invention is characterized in that each part is provided with a substantially annular conductor, which conductors are arranged in alignment side by side, while guide members which are rotatable about the common axis of the conductors are provided in a manner such that an electrically conductive endless wire or strip is guided from one of the conductors via the guide members to the other conductor and from there via the guide members again to the first-mentioned conductor.

In accordance with the invention this has the advantage that the wire or strip does not move locally both with respect to one annular conductor and to the other annular conductor.

It has been found that this construction does not give rise to sparks or to crackling, while by the choice of the diameter and the shape of the annular conductors the contact surface between the annular conductors and the wire or strip can be made sufiiciently large to keep the transition resistance low.

In a preferred embodiment of the invention the rotatable guide members also consist of approximately annular conductors arranged in alignment side by side and, moreover rotatable about their common axis.

The invention will be described more fully with reference to one embodiment. The approximately annular conductors are shaped in the form of circular discs.

The FIGURE shows the discs 1 and 2 in a coaxial position side by side. The disc 1 is rotatable about the associated shaft 3 and the disc 2 is stationary. The discs 4 and 5 are also arranged in alignment side by side and rotatable about their common shaft 6. The shaft 6 is journaled so as to be revolvable about the common shaft of the discs 1 and 2. The shaft 6 is preferably at the same distance from the disc 1 and the disc 2, While it crosses the shaft 3 at right angles. The diameter of the discs 4 and 5 is approximately equal to the distance between the discs 1 and 2. The diameter of the discs 1 and 2 is approximately equal to the distance between the discs 4 and 5. An electrically conductive wire 7 is guided from the disc 1 via the disc 4 to the disc 2 and from there via the disc 5 again to the disc 1. The shaft 6 is journaled by means of an arm 8 on a shaft 9, which is in line with the shaft 3. If the disc 1 rotates with a speedof, for example, 2x in the direction of the arrow 10, the arm will revolve with the discs 4 and 5 about the shaft 9 with a speed x. Consequently, the wire 7 will roll clear from all discs, so that the wire is not dragged along one of the discs. Thus a satisfactory electrical contact between the discs 1 and 2 is obtained by means of the wire 7.

The approximately annular conductors of the above embodiment, shaped in the form of the discs 1 and 2, may have a polygonal, for example a hexagonal form in order to increase the contact pressure. In the scope of the invention the external corners of a star-shaped conductor should be considered together as an approximately annular conductor. Moreover, the external profile of these conductors may be chosen, with respect to the shape of the section of the endless conductor, so that the electrical contact is self-cleaning during operation, for example by providing a V-groove with a sharp apex or by providing contact springs or points, along which the endless conductors rub each time.

As a matter of fact more of these systems may be arranged between the relatively rotatable parts, the guide members of these systems being revolvable about the common axis relatively to one another through suitable angles, so that a plurality of independent electric connections is obtained.

What is claimed is:

1. Apparatus for conducting electric current between a fixed conductor and a rotatable driven conductor comprising a rotatable driven conductor, a fixed conductor and means to electrically connect said conductors; said means characterized by a continuous conducting strip driven by said rotatable conductor, a first rotatable guide member driven by said strip and guiding said strip from said rotatable conductor to said fixed conductor, a second rotatable guide member driven by said strip and guiding said strip from said fixed conductor to said rotatable conductor and rotatable means intermediate said fixed and rotatable conductor and coaxial therewith supporting said first and second guide members for orbital movement about said conductors,

2. An electric connector comprising coaxial fixed and rotatable conductors in spaced parallel relation, a pair of rotatable disc shaped guide members, a shaft rotatably mounting said guide members, a shaft pivotally mounted intermediate and coaxial with said conductors, means joining both said shafts for mounting said first-mentioned shaft for orbital movement about said conductors, an electrically conductive endless strip being guided from one of the conductors substantially around one of the guide members to the other conductor, and then substantially around the other guide member and back to said one conductor.

3. An electric connector comprising fixed and rotatable conductors which are spaced coaxially relative to one another, a pair of guide members, means for mounting said guide members for rotation about a common axis displaced laterally from the axis of said conductors, means for supporting said first mentioned means for revolution about the common axis of said conductors, an electrically conductive endless strip being guided from one of the conductors substantially around one of the guide members to the other conductor, and then substantially around the other guide member and back to said one conductor.

4. An electric connector as claimed in claim 3 wherein said conductors are annular discs.

5. Apparatus for conducting electric current between a fixed conductor and a rotatable driven conductor comprising a rotatable driven conductor, a fixed conductor coaxial therewith and means to electrically connect said conductors; said means characterized by a continuous conducting strip driven by said rotatable conductor, a first rotatable guide member driven by said strip and guiding said strip from said rotatable conductor to said fixed conductor, a second rotatable guide member driven by said strip and guiding said strip from said fixed conductor to said rotatable conductor, and means supporting said first and second guide members for circular orbital movement about the common axis of said conductors.

References Cited in the file of this patent UNITED STATES PATENTS 2,276,983 Jonas Mar. 17, 1942 2,364,323 Staude et al. Dec. 5, 1944 2,364,325 Staude et a1 Dec. 5, 1944 2,467,758 Lindenblad Apr. 19, 1949 OTHER REFERENCES 

